Display device with alignment markers

ABSTRACT

A substrate of a display device is provided with markers which ensure accurate alignment of the display device with respect to a housing of an electronic device which includes the display device. By using e.g. V-shaped notches in the substrate edge, easy mechanical alignment with other parts of the device is obtained.

FIELD OF THE INVENTION

The invention relates to a display device comprising a first substrateprovided with an electric conductor pattern for pixels. The inventionalso relates to a device provided with such a display device. Theinvention further relates to a method of manufacturing such a displaydevice.

BACKGROUND OF THE INVENTION

Display devices of the type described, particularly liquid crystaldisplay devices, are commonly used in, for example, measuring equipmentbut also in, for example, portable telephones. Moreover,electroluminescent display devices, based on (organic) LEDs find anincreasingly wider application.

With the on-going miniaturization of electronics, it is possible torealize an increasing amount of drive electronics on the substrate.However, there is a tendency to manufacture the actual display panel(display section) as a standard component. If such a standard componentis mounted by a client into an apparatus, for example, by soldering onthe support (for example, a printed circuit board or another type ofsubstrate provided with conducting (connection) tracks), or by clamping,increasingly stricter requirements are imposed on the positioning of thedisplay panel to be provided with respect to the (further) device(mobile telephones, organizers, palmtop computers, etc.) in which thedisplay panel is incorporated. The tolerance does not only define theaccuracy with which conducting tracks of the panel and parts of thefurther device are aligned with each other (and hence resistancevariations), but also the maximum quantity of surface which must bereserved for the display panel in the device. Since, due to themanufacturing process, the glass edges in, for example, LCD panels havean undefined edge (tolerance ±0.2 mm) in, for example, LCD panels, thedisplay panel can no longer be introduced into the further devicewithout special precautions when increasingly narrower contact tracks(of the order of 40 μm) are used.

SUMMARY OF THE INVENTION

It is, inter alia, an object of the present invention to provide asolution to the above-mentioned problem. To this end, a display deviceaccording to the invention is characterized in that, for aligning theconductor pattern with respect to at least a part of a device foraccommodating the display device, the substrate is provided along itsedge with at least a marker.

As will be further described, the marker is provided very accuratelywith respect to the conductor pattern. This provides the possibility ofusing the conductor pattern (or a related pattern such as, for example,an alignment pattern used during a part of the manufacture which is notnecessarily a part of the conductor pattern) indirectly as an alignmentmark in the final assembly. This has the advantage that the client doesnot need to use expensive equipment (for example, a so-called “visionsystem”) for aligning the display panel with respect to the furtherdevice by means of the usually transparent (ITO) conductor pattern orfurther pattern. Moreover, the placement tolerance is reducedconsiderably and accurate straightening of the substrate edges (forexample, by means of laser cutting) is not necessary.

The markers are formed as, for example, recesses (having a U-shape, aV-shape, a semi-circular shape or a trapezoidal shape) in an edge of thesubstrate. Alignment is then effected, for example, by abutment with acounter element in the further device comprising, for example, anoptical waveguide. A preferred embodiment of a display device accordingto the invention is characterized in that the substrate is substantiallyrectangular and in that two edges of the substrate, enclosing an angle,have recesses. Fixation in the further device by fixing the panel in twodirections is thereby possible.

A method of manufacturing a display device, in which an initialsubstrate is subjected to at least a substrate treatment in which it isprovided with a pattern for realizing at least a part of the displaydevice, whereafter the initial substrate is divided, if necessary, intoa plurality of substrates of display devices for forming the displaydevice is characterized in that, with a pattern on the substrate asalignment mark, at least one edge of the substrate of the display deviceis provided with a visible marker.

These and other aspects of the invention are apparent from and will beelucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a diagrammatic plan view of a plane through a part of a deviceaccording to the invention,

FIG. 2 is a cross-section taken on the line II—II in FIG. 1,

FIG. 3 is a cross-section taken on the line III—III in FIG. 1, while

FIG. 4 is a plan view of a part of a display device according to theinvention, and

FIG. 5 shows a further variant.

The Figures are diagrammatic and not drawn to scale. Correspondingelements are generally denoted by the same reference numerals.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a plan view of a plane within a device 1 which is accommodatedin a housing 2 (FIGS. 2, 3). The device is, for example, an electronicinstrument such as a mobile telephone, or another instrument having adisplay function. For displaying (alphanumerical) information, thedevice is provided with a display device, in this example a liquidcrystal display device, but a display device based on (organic) LEDs isalternatively possible. The liquid crystal display device in thisexample is shown in a simplified form by means of two transparentsubstrates 3, 4 and a sealing edge 5 between which liquid crystalmaterial 6 is present. In this example, the liquid crystal displaydevice is of the transmissive type. The device 1 therefore comprises abacklight 7 which is shown in a simplified form by means of a lamp 8 anda waveguide 9. If necessary, the substrate 3 is provided with one ormore drive ICs 10 which provide the device with drive voltages. Forexample, transparent electrodes 11 on the substrate 4 are connected in agenerally known manner to said IC 10 via interconnections 12. For thesake of simplicity, FIGS. 1, 2 only show two transparent electrodes 11.Further drive electronics, for example, realized on a printed circuitboard 13 and other functions of the device to be operated by means ofkeys 14 shown diagrammatically are also omitted for the sake ofsimplicity. The printed circuit board 13 has an aperture 15 to passlight from the backlight 7. The housing 2 also has a window 16 at thearea of the part to be displayed of the display device so as to protectit from exterior influences.

Although the housing 2 is shown as one assembly in FIGS. 2, 3, itusually consists of a plurality of parts which are secured together inthe final assembly by means of adhesive, clamping or screwingconnections or other connections. A critical step in the combination ofthe composite parts is, inter alia, the mechanical alignment of thedisplay device (the assembly of, inter alia, the transparent substrates3, 4, sealing edge 5, and liquid crystal material 6) or a part thereofwith respect to a further part of the device 1, for example, withrespect to an almost completed device, including printed circuit board13 and backlight 7, particularly if these two parts are made at separatelocations or are supplied by a plurality of suppliers. Usually, thedisplay device is the last to be provided in the device by sliding itinto a part of the housing and clamping (clicking) it into position,whereafter the housing is closed. To determine the correct location forclicking the display device into position, one of the substrates isusually moved against a counter element or alignment member 17. In, forexample, LCD panels, the edges of the substrates are not accurate due tothe manufacturing process (tolerance ±0.2 mm). For narrow contacttracks, such an inaccurate connection of the display panel to the otherpart of the device causes problems (for example, high connectionresistances).

According to the invention, the substrate 4 in this example has tworecesses 18 which have been provided with great accuracy with respect tothe wiring pattern (the transparent electrodes 11) or another alignmentmark on the substrate 4. The recesses are obtained by means of millingor by means of another suitable mechanical operation (laser cutting).This mechanical operation is performed with the wiring pattern 11 as analignment mark or an alignment mark 19 which was used during manufactureof the display device (FIG. 4). Since milling takes place with greataccuracy (±50 μm), the distance d₁ between the alignment mark 19 and thealignment pen (the counter element 17) is defined very accurately afterthe display device has been clicked into position in the further device.Possible variations in the edge 20, 20′ of the substrate, which mayincrease to approximately 0.4 mm, do not affect the position of thedisplay section of the substrate 4 with respect to this counter element17. The position of the transparent electrodes 11 with respect to, forexample, an electrode 21 on the printed circuit board, and moreparticularly the position of the actual display elements with respect toan envelope, such as the housing 2, is thereby defined very accurately.For a very accurate positioning, preventing rotation of the displaydevice, two edges of the substrate, enclosing an angle, are preferablyprovided with recesses as are shown in FIG. 5. In FIG. 5, the recesseshave a V-shape and a trapezoidal shape, respectively, but a U-shape or asemi-circular shape is alternatively possible.

A display device is manufactured in generally known manner by subjectinga first initial substrate to a plurality of operations. The initialsubstrate may have a single alignment mark. After completion, a secondinitial substrate which has also been subjected to a plurality ofoperations and after providing sealing edges, these substrates arecombined (in the case of LCDs) and subsequently one or more displayelements are formed by means of so-called “scratching and breaking”. Theseparate cells thus obtained are filled with the liquid crystal materialbefore or after “scratching and breaking”. Subsequently, at least anedge of the substrate of the cell is provided with a marker, with apattern on the substrate as an alignment mark. The alignment mark may bea part of the display device, for example, a (part of a) wiring pattern11, but also a separately provided alignment mark 19 (per cell).

To this end, one or more edges of the substrate are provided withmarkers such as recesses 18. As described above, mechanical alignmentwith respect to the further device is now possible in a very accurateway.

If desired, the marker may be alternatively an optical mark, forexample, a (visible) dot which is very accurately aligned with respectto the conductor pattern of the display device. This is visually alignedwith respect to, for example, an alignment mark or wiring patterns onthe printed circuit board 13.

A marker (recess 18) once provided is used to advantage in furtheroperational steps (after completion of the cell in this example) as analignment element for further manufacturing steps such as, for example,providing polarizers, defining bond flaps, etc.

The invention is of course not limited to the examples shown, butseveral variations are possible within the scope of the invention. Forexample, the recesses 18 may also be provided in the substrate 3 inwhich, if necessary, the counter elements 17 have a limited height. An(organic) light-emitting device ((O)LED) may also be chosen as a displayelement.

In summary, the invention provides measures of arranging a displaydevice with great accuracy in a larger assembly.

The invention resides in each and every novel characteristic feature andeach and every combination of characteristic features.

What is claimed is:
 1. A display device comprising a first substrateprovided with an electric conductor pattern for pixels, wherein, foraligning the conductor pattern with respect to at least a part of anapparatus for accommodating the display device, the substrate isprovided along a first edge with at least a first marker and along asecond edge with at least a second marker; said first edge intersectingsaid second edge.
 2. A display device as claimed in claim 1, whereinsaid at least first marker includes a recess.
 3. A display device asclaimed in claim 2, wherein the recess has a U-shape, a V-shape, asemi-circular shape or a trapezoidal shape.
 4. A display device asclaimed in claim 1, wherein the substrate is substantially rectangular,and wherein said at least first marker and said at least second markerinclude recesses.
 5. An apparatus provided with the display device asclaimed in claim 1, wherein the apparatus has at least an alignmentelement at a location of said at least marker of the substrate.
 6. Anapparatus provided with the display device as claimed in claim 1,wherein the apparatus has counter elements at a location of a recess ofthe substrate.
 7. A method of manufacturing a display device comprising:subjecting an initial substrate to at least a substrate treatment inwhich said initial substrate is provided with a pattern for realizing atleast a part of the display device, dividing the initial substrate intoa plurality of substrates of display devices for forming the displaydevice, with a pattern on the substrate as an alignment mark, providinga first edge of the substrate of the display device with a first marker,and providing a second edge of the substrate with a second marker; saidfirst edge intersecting said second edge.
 8. A method as claimed inclaim 7, further comprising using the pattern for realizing at least apart of the display device as an alignment mark.
 9. A method as claimedin claim 7, further comprising providing a recess in at least said firstedge of the substrate.
 10. A method as claimed in claim 9, furthercomprising using at least said first marker as an alignment mark in foraccommodating the display device in a further device.
 11. A method asclaimed in claim 9, further comprising using at least said first markeras an alignment mark in the steps of manufacturing the display device.12. A method as claimed in claim 7, further comprising providingrecesses in said first edge and said second edge of the substrate,wherein the substrate is substantially rectangular.
 13. A display for adevice having at least two alignment members, said display comprising asubstrate having a pattern with at least two intersecting edges thatform a corner; wherein each of said at least two intersecting edges hasa recess substantially near said corner; said recess of each of said atleast two intersecting edges abutting against a respective one of saidat least two alignment members for aligning said display in said device.